1. Field of the Invention
The present invention relates to an X-ray fluorescence spectrometer having an optical system by so-called parallel beam method.
2. Description of the Prior Art
In the X-ray fluorescence analysis, for example, a sample is in the form of a disc of a predetermined size, after having been retained by a predetermined sample holder, placed on a sample support table and is then irradiated by primary X-rays emitted from an X-ray source such as an X-ray tube so as to impinge upon a surface of such sample. In general, in order to increase the sensitivity of the spectrometer, the X-ray source is positioned as close to the sample as possible. Considering, however, that it is at the same time necessary for the X-ray source not to disturb and interfere the field of view of the detecting means aimed at the sample surface, the X-ray source such as the X-ray tube is generally disposed slantwise relative to the sample surface.
However, it has been found that if the distance between the X-ray source and the sample surface is chosen to be very small, slight change of such distance as a result of the presence of irregularities, warps or deflections up to about 1 mm on the sample surface brings about an unnegligible change in intensity of the fluorescent X-rays emitted from the sample, resulting in insufficient improvement over the analyzing accuracy.
Accordingly, the present invention has been devised to substantially eliminate the inconveniences inherent in the prior art X-ray fluorescence spectrometer and is intended to provide an improved X-ray fluorescence spectrometer capable of providing a stable fluorescent X-ray intensity.
In order to accomplish the foregoing object, the present invention provides an X-ray fluorescence spectrometer which includes a sample support table for supporting thereon a sample to be analyzed, an X-ray source for radiating primary X-rays so as to impinge slantwise on a flat surface of the sample and including a primary X-ray limiting diaphragm having an aperture for limiting a bundle of the primary X-rays emitted therefrom towards the sample surface, and a detecting means positioned so as to aim slantwise at the sample surface for measuring an intensity of fluorescent X-rays emitted from a site of interest of the sample. The detecting means includes a field limiting diaphragm having an aperture for limiting a field of view encompassing the sample surface and a soller slit for collimating the fluorescent X-rays emitted from the sample. The aperture of the primary X-ray limiting diaphragm is of a shape effective to allow change in intensity of the fluorescent X-rays measured by the detecting means to be not higher than 1% in the event that a height of the sample surface relative to the X-ray source and the detecting means changes 1 mm at maximum.
According to the present invention, since the aperture of the primary X-ray limiting diaphragm is of a shape uniquely designed as to allow change in intensity of the fluorescent X-rays measured by the detecting means to be not higher than 1% in the event that a height of the sample surface relative to the X-ray source and the detecting means changes 1 mm at maximum, the stable fluorescent X-ray intensity can be secured regardless of the presence of the irregularities or the like on the sample surface and, accordingly, the analyzing accuracy can be sufficiently increased.
Also, a similar effect can be equally obtained even if the respective apertures of the primary X-ray limiting diaphragm and the field limiting diaphragm are uniquely designed and shaped.
For example, the aperture of the primary X-ray limiting diaphragm may be of a substantially round shape with a portion thereof blocked, the aperture of the field limiting diaphragm may be of a substantially oval shape with a portion thereof blocked.
Preferably a rotary mechanism is employed to rotate the sample.